Final answer:
Chemical analysis of non-refrigerated blood samples should be completed within 3 hours. During the first hour, blood clots and serum can be harvested, a crucial step before analytes degrade or are affected by enzymatic activities or microbial growth.
Step-by-step explanation:
Without refrigeration, chemical analysis of blood samples should be completed within 3 hours to ensure the integrity of the sample. During the first hour in a glass tube, the blood begins to clot, and the serum (the liquid part of the blood that can be used for testing) can be separated by a process such as centrifugation. Factors such as temperature and the presence of enzymes or microbes can affect the stability of the blood sample, hence the importance of timely analysis. This urgency is due to potential changes in the sample, such as enzymatic activity or microbial growth, which can occur at a typical incubation temperature of 37°C. In a typical analysis scenario, samples like blood or urine are often prepared differently; for example, plasma samples from blood may be preserved with methanol before analysis, and urine samples might be analyzed with no prior preparation.